Veterinary Dermatology 2006, 17, 45– 50
Blackwell Publishing Ltd
The impact of body site, topical melatonin and brushing on hair regrowth after clipping normal Siberian Husky dogs
SANDRA F. DIAZ, SHEILA M. F. TORRES, SANDRA A. F. NOGUEIRA,
SOPHIE GILBERT and CARL R. JESSEN
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Paul,
(Received 9 January 2005; accepted 18 November 2005)
The aims of this study were to determine the impact of body site, vigorous brushing and topical mela-
tonin treatment on hair regrowth after clipping normal dogs. Siberian Husky dogs were randomly assigned tothree groups of eight dogs each. All dogs had the lumbosacral region and both lateral thighs clipped. The leftthigh and lumbosacral area received no treatment and were compared in all 24 dogs. Eight dogs had the rightthigh treated with 0.1% melatonin twice daily for 2 months, and hair regrowth was compared with the left thigh.Eight dogs had the right thigh brushed twice daily for 2 months, and hair regrowth was compared with the leftthigh. Eight dogs had neither thigh treated. Hairs were plucked before and 2 months postclipping, and the pro-portion of hair growth from the original length was calculated and compared as described above. Biopsy sampleswere collected before and after treatment to determine if brushing induced dermal inflammation and melatoninincreased the proportion of anagen follicles. Proportionally, left thigh hairs were significantly longer comparedto lumbosacral hairs 2 months postclipping. No significant differences in hair regrowth were noted between thenontreated thigh and the thigh treated with melatonin or brushed. No significant difference in dermal inflam-mation was noted before and after brushing. No significant differences were observed in the proportion of anagenfollicles before and after topical melatonin treatment. Our results showed that the hairs in the lumbosacral regionwere proportionally shorter than lateral thigh hairs 2 months postclipping. Moreover, topical melatonin andbrushing had no impact on hair regrowth after clipping normal dogs.I N T RO D U C T I O N
Skin histopathology of dogs that experience delay in
hair regrowth postclipping shows hair follicle arrest.10
The delay in hair regrowth after clipping is a well-
An interesting and frequently observed finding in these
recognized but a poorly understood condition that worries
cases is the regrowth of tufts of hairs at the biopsy site
many pet owners who take pride in their pet's coat. Con-
a few weeks after the procedure.10 This has also been
cerned owners frequently ask veterinarians how they can
reported in follicular arrest associated with endocrine
help accelerate hair regrowth. Few studies have evaluated
alopecia, suggesting that local inflammation stimulates
factors that influence canine hair growth and those that
hair regrowth.11,12 However, to our knowledge, no
exist are uncontrolled and include few dogs.1–4
controlled studies have been conducted to determine
Hair growth is controlled by complex interactions
whether induced skin inflammation stimulates hair
between endogenous and exogenous influences.5–7 It
has often been observed that hairs on the lumbosacral
Melatonin is thought to play either a direct or an indi-
region grow more slowly than hairs on the lateral thigh
rect role in the neuroendocrine control of moulting and
when both areas are clipped for hip surgery. Troncy
hair growth in mammals.13–15 In dogs, oral melatonin
et al. noticed while investigating two epidural anaes-
has been used to treat various forms of alopecia, such as
thesia protocols that 11% of the dogs included in the
recurrent flank alopecia, pattern baldness and alopecia-
study experienced a delay in hair regrowth on the lum-
X of the Nordic breeds, with variable success.16–19
bosacral region after clipping.8 Preliminary data from
Researchers have investigated the therapeutic use of
a study conducted in Greece indicated that neither
melatonin in humans as well. In a recent study per-
epidural anaesthesia nor scrubbing or clipping seems
formed in women with either androgenic or diffuse
to affect hair regrowth in this area.9 These results seem
alopecia, topically applied 0.1% melatonin led to a
to confirm the frequent anecdotal finding that body
significant increase in anagen hair rate when compared
region has an impact on hair regrowth postclipping.
with placebo.20 It is tempting to investigate the impactof topical melatonin on hair regrowth in dogs withpostclipping follicular arrest. Topical application of
Correspondence: Dr Sheila M. F. Torres, Department of Small
melatonin has been shown to limit the drug effect to
Animal Clinical Sciences, College of Veterinary Medicine, University
treated areas, thus allowing higher concentrations at
or Minnesota, C339 Veterinary Hospitals, 1352 Boyd Avenue, SaintPaul, MN 55108, USA. E-mail: [email protected]
the treated sites, which may increase the chances of
2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology
SF Diaz et al.
success.20 Therefore, the aim of this study was to deter-
of the neutroceutical 0.1% melatonin in alcohol (99.1%
mine the impact of body site, vigorous brushing and
bulk melatonin powder Village Drug, Northfield, MN,
topical melatonin treatment on hair regrowth after
USA),20 and the left lateral thigh served as control.
clipping the hair coat of healthy Siberian Husky dogs.
Based on a pilot study, the amount of solution necessaryto cover the clipped area was determined to be approxi-mately 0.5 mL. A spray bottle capable of delivering
0.1 mL per pump was used to apply the melatoninsolution; therefore, five pumps of melatonin solution
Study population
were applied to the clipped area on the right thigh twice
Privately owned intact male Siberian Husky sled dogs
daily for 2 months. As with group 2, hair regrowth
were considered for inclusion in the study. This group of
between the right and left thighs and between the
dogs was deliberately chosen because the dogs were of the
lumbosacral area and the left thigh was compared.
same breed and gender, kept in the same environmentalconditions and fed the same diet for the duration of the
Follow-up of hair regrowth
study, which was conducted during a single season (July
Before clipping, hairs representing each of the three
and August 2004). Therefore, we were able to control
clipped sites were plucked by one of the investigators
for factors that could potentially influence hair regrowth,
(SD), with the necessary caution to preserve the hair
such as breed, gender, temperature, day light, diet and
structure. Before measuring, the hairs were scrutinized
season.7 Inclusion criteria were the lack of systemic or
under the microscope to assure that the hair shafts
dermatological diseases as evaluated by complete history
were intact and straight. From this hair pool, 10
and thorough physical examinations. Blood was drawn
primary and 10 secondary hair shafts were mounted in
from all dogs prior to the beginning of the study and
a microscope slide using a 10-mm wide, double-sided
submitted for serum total thyroxine concentrations. Dogs
adhesive tape and measured in centimetres from tip to
were excluded from the study if serum total thyroxine
root with a ruler. The average length of primary and
concentrations were below the normal reference range
secondary hairs was considered as representative of the
for the Veterinary Diagnostic Laboratory at the University
sites that were followed up postclipping (lumbosacral
of Minnesota and if they were receiving medications
area, and right and left lateral thighs). At the end of the
that could affect hair growth (e.g. progestins, oestrogen,
study, one of the investigators (SD) plucked hairs from
androgens, melatonin, glucocorticoids and -thyroxine).
the clipped areas of all 24 dogs. The proportion of hair
The study was approved and overseen by the Institu-
growth from the original length for each clipped area
tional Animal Care and Use Committee of the University
was calculated and compared as described previously
of Minnesota.
for each group.Groups and proceduresBiopsy collection
Twenty-four dogs met the inclusion criteria and were
Two skin biopsy samples were collected from the right
randomly assigned to three groups of eight dogs each.
lateral thigh from all dogs in groups 2 and 3. One sample
All dogs in each group had an area of 6 × 8 cm clipped
was collected before and one after the last treatment
on the lumbosacral region and both lateral thighs. The
to determine whether any dermal inflammation was
areas clipped were marked on the dog's skin with a per-
induced by brushing (group 2) and whether melatonin
manent marker through a template containing a 6 × 8 cm
application influenced the hair cycle phases (group 3).
precision-drilled rectangle. The left lateral thigh and the
Before treatment, the biopsy sample was collected from
lumbosacral area were not treated in any of the 24 dogs.
an area adjacent to the clipped site to avoid inflamma-tion induced by the biopsy procedure influencing hair
Group 1. No treatment was administered to the dogs in
regrowth of the treated area. After the last treatment,
this group. Hair regrowth of lumbosacral area was
the biopsy was collected from the treated site. Samples
compared to that of left thigh. The right thigh served
were collected with a 6-mm punch biopsy instrument
as control for the left thigh.
using subcutaneous 2% lidocaine. For group 2, thesamples were sectioned longitudinally to assess dermal
Group 2. All eight dogs had the clipped area on the
inflammation. Samples from group 3 were transversally
right lateral thigh vigorously brushed twice daily for
sectioned for morphometric assessment of hair cycle
30 s using a rubber brush (Zoom /Groom®, Kong
phases. Skin biopsy samples were routinely processed
Company, Golden, CO, USA) for the 2-month study
for histopathology and stained with haemotoxylin and
duration. Based on a pilot study, the brushing period
eosin stain (H&E).
was shown to induce the desired mild skin irritation.The left lateral thigh served as control. Hair regrowth
between the right and left thighs and between the
To assess the degree of dermal inflammation in group
lumbosacral area and the left thigh was compared.
2, all inflammatory cells present within the dermis ofthe whole tissue section were counted at ×40 magnifi-
Group 3. All eight dogs had the clipped area on the
cation. In fields containing glands and hair follicles, only
right lateral thigh treated with a compounded solution
intervening dermal regions were counted. Intravascular
2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology

Body site, melatonin and brushing effect on hair regrowth
and fibroblastic cells were excluded from the count.The degree of inflammation was classified as 0 – absent;1 – low (< 10 inflammatory cells/section); 2 – medium(10–50 inflammatory cells/section); or 3 – high (> 50inflammatory cells/section). The investigator per-forming the counting (SD) was blind, regarding whetherthe histopathological section referred to before or afterbrushing.
Morphometric assessment of hair follicle cycle phases
Figure 1. Average percentage of hair regrowth 2 months after
in group 3 was performed in transversally sectioned
clipping the lumbosacral area and left lateral thigh of 24 normal Siberian Husky dogs. Primary and secondary hairs were evaluated.
skin biopsies as previously described.21,22 Briefly, 40 –50
LSP = lumbosacral area, primary hairs; LTP = left thigh, primary
transversal sections per biopsy sample were initially
hairs; LSS = lumbosacral area, secondary hairs; LTS = left thigh,
reviewed to select follicular units showing sebaceous
secondary hairs. *Significantly (P = 0.002) different from LTP.
glands and arrector pili muscle. The presence of these
†Significantly (0.026) different from LTS.
structures indicated that the hair follicles were sectionedat the mid-isthmus level, which allowed the determina-tion of the hair follicle phases.23 A follicular unit wasdefined as a group of three compound follicles.21,23Anagen and telogen hair follicles were counted in fivefollicular units per biopsy sample.21 The investigatorperforming the counting (SD) was blind, regardingwhether the histopathological section referred to beforeor after melatonin treatment.Figure 2. Average percentage of hair regrowth after 2 months of
Paired Student's t-test was used to compare the pro-
clipping the left and right lateral thighs of eight normal Siberian
portion of hair regrowth postclipping between the lum-
Husky dogs. The right lateral thigh was also brushed twice daily for
bosacral area and the left lateral thigh on all 24 dogs.
the 2-month period. Primary and secondary hairs were evaluated. RTP = right thigh, primary hairs; LTP = left thigh, primary hairs;
Paired Student's t-tests was also used to compare the
RTS = right thigh, secondary hairs; LTS = left thigh, secondary
proportion of hair regrowth between the brushed thigh
hairs. No significant difference was found between RTP and LTP
(right) and the control thigh (left) in group 2, and
(P = 0.84) or between RTS and LTS (P = 0.40).
between the melatonin-treated thigh (right) and thecontrol thigh (left) in group 3. Wilcoxon signed rankstest was used to compare the score given to dermal
and brushing the right thigh was 3.20 and 2.46 cm,
inflammation before and after brushing the right leg of
and after only clipping, the left thigh was 3.10 and
the eight dogs in group 2 and to compare the proportion
2.21 cm, respectively. No significant difference was
of anagen follicles before and after melatonin treatment
found in the proportion of primary (P = 0.84) or
of the eight dogs in group 3. A value of P < 0.05 was
secondary (P = 0.40) hair regrowth when the brushed
considered significant. All analyses were preformed
thigh (right thigh) was compared with the control thigh
using    (SAS Institute,
Cary, NC, USA).
The average length of primary hairs before and
2 months after clipping and treating the right thighwith melatonin was 3.80 and 2.15 cm, and after only
clipping, the left thigh was 3.8 and 2.09 cm, respect-ively. The average length of secondary hairs before and
The average length of primary hairs before and 2 months
2 months after clipping and treating the right thigh
after clipping the lumbosacral area was 5.70 and
with melatonin was 3.00 and 2.36 cm, and after only
2.95 cm, and the left lateral thigh was 3.30 and 2.10 cm,
clipping, the left thigh was 3.10 and 2.26 cm, respect-
respectively. The average length of secondary hairs
ively. No significant difference in the proportion of
before and 2 months after clipping the lumbosacral
primary (P = 0.52) or secondary (P = 0.15) hair regrowth
area was 4.40 and 2.79 cm, and the left lateral thigh was
was seen when comparing the melatonin-treated thigh
2.80 and 2.03 cm, respectively. Proportionally, primary
(right thigh) with the control thigh (Fig. 3).
(P = 0.002) and secondary (P = 0.026) hairs were sig-
Before brushing in group 2, the degree of dermal
nificantly longer on the left lateral thigh compared to
inflammation was low in one dog and medium in seven
the lumbosacral region 2 months postclipping (Fig. 1).
dogs. Two months after twice-daily brushing, the degree
The average length of primary hairs before and 2
of dermal inflammation was low in one dog and medium
months after clipping and brushing the right thigh was
in six dogs. These differences were not significant (P =
3.50 and 2.35 cm, and after only clipping, the left thigh
1.00). Dermal inflammation could not be assessed in
was 3.50 and 2.38 cm, respectively. The average length
one dog postbrushing because of poor tissue process-
of secondary hairs before and 2 months after clipping
ing. In group 3, no significant differences were observed
2006 The Authors. Journal compilation 2006 European Society of Veterinary Dermatology

As well as being president of the Conditional Immortality Association I also pastorThe Church of Christ (L&A) in Takanini and as part of my work with the AdventChristian Conference of New Zealand, the Randwick Park Christian Life Church.The Randwick Park Christian Life church meets in a Council run Community house.But we are not the only "spiritual" group that uses the building. There is our smallgroup of Bible believing Christians who meet there. There are three other groups ofspiritualists and mediums that meet there. These people are convinced that thereexist invisible, superhuman "spirit guides" wanting to make contact with people hereon earth. These people are convinced that it is possible and even desirable to makecontact with the spirits of human beings that have lived and died here on earth.

RÉMY MARTIN NIGERIA – WEBSITE T&CS: 1. Information on how to enter and the prize(s) form part of these Terms and Conditions. Participation in this promotion is deemed acceptance of these Terms and Conditions. 2. Entry is only open to Nigerian residents who are aged 18 years or over. Winning entries will only be selected from individuals who are able to come to Lagos to redeem their prizes. Employees (and their immediate families) of the Promoter and agencies associated with this promotion are ineligible to enter.